Arenesulfinic acids, reaction with

The [3 + 2] addition of type IIbd is a significant method for synthesis of both simple and complex pyrrole derivatives. One manifestation of this pattern is seen in the base-catalyzed condensation of tosylmethyl isocyanide with alkenes having strong electron-accepting substituents. The aromatization by elimination of the arenesulfinic acid occurs under the reaction conditions (equation 117) (72TL5337). This reaction can be applied to the synthesis of 2,3,4-trisubstituted pyrroles by using C-alkylated tosylmethyl isocyanides or AT-tosyl-methyl-51-methylthioimidates (77H(7)77, 8IJHCII27). 

The reaction of palladium(II) complexes with arenesulfinic acids or their salts to yield the organic biaryls appears to proceed by formation of palladium sulhnato compounds and their desulfination 53a). 

Treatment of arenesulfinate salts with Cu2+, Mn3+, or Ce4+ generates arenesulfonyl radicals, via single electron oxidation. Thus, reaction of alkene (50) with p-TsNa in the presence of Cu(OAc)2 in AcOH gives p-tolyl allyl sulfone (51) through the addition of a toluenesulfonyl radical onto alkene, oxidation of the formed carbon-centered radical with Cu2+, and then deprotonation (eq. 4.20a). This reaction requires acidic conditions for effective oxidation with Cu2+ or Mn3+ [53-58]. Eq. 4.20b is the same addition... 

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